c# - StorageFile.OpenAsync 中的 UnauthorizedAccessException

Question

我用下面的代码下载/保存了一张图片，稍后打开，但是在后面的OpenAsync中，抛出了UnauthorizedAccessException，看起来是文件没有关闭，实际上IRandomAccessStream/DataWriter已经被处理掉了。

HttpClient httpClient = new HttpClient();
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, "http://www.silverlightshow.net/Storage/Users/nikolayraychev/Perspective_Transforms_4.gif");
HttpResponseMessage response = await httpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead);

//Write Image File
StorageFile imageFile = await ApplicationData.Current.LocalFolder.CreateFileAsync("test.gif", CreationCollisionOption.ReplaceExisting);
using (IRandomAccessStream fs = await imageFile.OpenAsync(FileAccessMode.ReadWrite))
{
    using (DataWriter writer = new DataWriter(fs.GetOutputStreamAt(0)))
    {
        writer.WriteBytes(await response.Content.ReadAsByteArrayAsync());
        await writer.StoreAsync();
        writer.DetachStream();
        await fs.FlushAsync();
    }
 }

 StorageFile imageFile1 = await ApplicationData.Current.LocalFolder.GetFileAsync("test.gif");
 //Exception is throwed here
 using (IRandomAccessStream stream = await imageFile1.OpenAsync(FileAccessMode.Read))
 {
     BitmapImage img = new BitmapImage();
     img.SetSource(stream);
}

Answer 1

我有同样的问题，必须在完成之前显式处理流和文件对象。

    var file = await ApplicationData.Current.LocalFolder.CreateFileAsync(filename, Windows.Storage.CreationCollisionOption.ReplaceExisting);
    using (var fs = await file.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite))
    {
        var outStream = fs.GetOutputStreamAt(0);
        var dataWriter = new Windows.Storage.Streams.DataWriter(outStream);
        dataWriter.WriteString("Hello from Test!");
        await dataWriter.StoreAsync();
        dataWriter.DetachStream();
        await outStream.FlushAsync();
        outStream.Dispose(); // 
        fs.Dispose();
    }